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Find the net area and the area of the region bounded by \( y=10 \cos x \) and the \( x \)-axis between \( x=-\frac{\pi}{2} \) and \( x=\pi \). The net area is \( \square .( \) Simplify your answer.)

Ask by Pritchard Cook. in the United States
Feb 19,2025

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Tutor-Verified Answer

Answer

The net area is 30.

Solution

To find the net area and the area of the region bounded by the curve \( y = 10 \cos x \) and the \( x \)-axis between \( x = -\frac{\pi}{2} \) and \( x = \pi \), we will follow these steps: 1. **Identify the points where the curve intersects the \( x \)-axis**: This occurs when \( y = 0 \), or \( 10 \cos x = 0 \). Thus, we need to solve for \( x \): \[ \cos x = 0 \] The solutions in the interval \( [-\frac{\pi}{2}, \pi] \) are: \[ x = -\frac{\pi}{2}, \frac{\pi}{2} \] 2. **Calculate the area above the \( x \)-axis**: The area above the \( x \)-axis from \( x = -\frac{\pi}{2} \) to \( x = \frac{\pi}{2} \) can be calculated using the integral: \[ A_1 = \int_{-\frac{\pi}{2}}^{\frac{\pi}{2}} 10 \cos x \, dx \] 3. **Calculate the area below the \( x \)-axis**: The area below the \( x \)-axis from \( x = \frac{\pi}{2} \) to \( x = \pi \) can be calculated using the integral: \[ A_2 = \int_{\frac{\pi}{2}}^{\pi} 10 \cos x \, dx \] 4. **Calculate the net area**: The net area is given by: \[ \text{Net Area} = A_1 - A_2 \] Now, let's calculate these integrals step by step. ### Step 1: Calculate \( A_1 \) \[ A_1 = \int_{-\frac{\pi}{2}}^{\frac{\pi}{2}} 10 \cos x \, dx \] Calculating the integral: \[ A_1 = 10 \left[ \sin x \right]_{-\frac{\pi}{2}}^{\frac{\pi}{2}} = 10 \left( \sin\left(\frac{\pi}{2}\right) - \sin\left(-\frac{\pi}{2}\right) \right) = 10 \left( 1 - (-1) \right) = 10 \times 2 = 20 \] ### Step 2: Calculate \( A_2 \) \[ A_2 = \int_{\frac{\pi}{2}}^{\pi} 10 \cos x \, dx \] Calculating the integral: \[ A_2 = 10 \left[ \sin x \right]_{\frac{\pi}{2}}^{\pi} = 10 \left( \sin(\pi) - \sin\left(\frac{\pi}{2}\right) \right) = 10 \left( 0 - 1 \right) = -10 \] ### Step 3: Calculate the Net Area Now we can find the net area: \[ \text{Net Area} = A_1 - A_2 = 20 - (-10) = 20 + 10 = 30 \] ### Final Results - The net area is \( 30 \). - The area of the region bounded by \( y = 10 \cos x \) and the \( x \)-axis is \( A_1 + |A_2| = 20 + 10 = 30 \). Thus, the net area is \( \boxed{30} \).

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To find the net area and the area of the region bounded by \( y=10 \cos x \) and the \( x \)-axis between \( x=-\frac{\pi}{2} \) and \( x=\pi \), we first need to identify the behavior of the function within this interval. 1. **Finding the intersections**: - \( y = 10 \cos x \) intersects the \( x \)-axis where \( 10 \cos x = 0 \), or \( \cos x = 0 \). - This occurs at \( x = -\frac{\pi}{2} \) and \( x = \frac{\pi}{2} \) within the given interval. 2. **Calculating the net area**: - The area above the \( x \)-axis is between \( x = -\frac{\pi}{2} \) and \( x = \frac{\pi}{2} \), and the area below the \( x \)-axis is between \( x = \frac{\pi}{2} \) and \( x = \pi \). The function is positive from \( x = -\frac{\pi}{2} \) to \( x = \frac{\pi}{2} \) and negative from \( x = \frac{\pi}{2} \) to \( x = \pi \). 3. **Calculating the areas**: - Area from \( x = -\frac{\pi}{2} \) to \( x = \frac{\pi}{2} \): \[ A_1 = \int_{-\frac{\pi}{2}}^{\frac{\pi}{2}} 10 \cos x \, dx = 10 [\sin x]_{-\frac{\pi}{2}}^{\frac{\pi}{2}} = 10 [\sin(\frac{\pi}{2}) - \sin(-\frac{\pi}{2})] = 10 [1 - (-1)] = 20 \] - Area from \( x = \frac{\pi}{2} \) to \( x = \pi \): \[ A_2 = \int_{\frac{\pi}{2}}^{\pi} 10 \cos x \, dx = 10 [\sin x]_{\frac{\pi}{2}}^{\pi} = 10 [\sin(\pi) - \sin(\frac{\pi}{2})] = 10 [0 - 1] = -10 \] We take the absolute value since we want the area: \[ A_2 = 10 \] 4. **Net area**: \[ \text{Net Area} = A_1 + A_2 = 20 - 10 = 10 \] Thus, the net area is \( \boxed{10} \). The total area bounded by the curve and the \( x \)-axis is \( 20 + 10 = 30 \).

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